The British battle fleet, Vol. 2 (of 2) : its inception and growth throughout…
9. When a ship of the British Admiralty meets a ship of the Dominions,
the senior officer will have the right to command in matters of
ceremony or international intercourse, or where united action is agreed
upon, but will have no power to direct the movements of ships of the
other service unless the ships are ordered to co-operate by mutual
arrangement.